# Add new field based on another field
**URL:** https://discuss.elastic.co/t/add-new-field-based-on-another-field/160064
**Category:** Logstash
**Created:** [December 9, 2018, 7:08pm UTC](https://discuss.elastic.co/t/add-new-field-based-on-another-field/160064 "2018-12-09T19:08:12Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Ivan44785372](https://discuss.elastic.co/u/Ivan44785372)
#### Post date: [December 9, 2018, 7:08pm UTC](https://discuss.elastic.co/t/add-new-field-based-on-another-field/160064/1 "2018-12-09T19:08:12Z")
Hello.
I have such field in filebeat output docker.container.labels.app
it looks like this:
```auto
"docker" => {
"container" => {
"id" => "7549e137-3394-987d-f3cc-f79759851a62",
"labels" => {
"app" => "app1",
"env" => "production",
}
}
```
I want to set another field in logstash based on this field - docker.container.labels.app
I have such configuration:
```auto
filter {
if ("" in [docker.container.labels.app]) {
mutate {
add_field => { "app" => "unknown" }
}
} else {
mutate {
add_field => { "app" => [docker.container.labels.app] }
}
}
}
```
But it doesn't work. Can you help me ?
---
### Author:  [@Ivan44785372](https://discuss.elastic.co/u/Ivan44785372)
#### Post date: [December 9, 2018, 7:35pm UTC](https://discuss.elastic.co/t/add-new-field-based-on-another-field/160064/2 "2018-12-09T19:35:45Z")
Sorry. I found the solution.
add\_field =\> { "app" =\> "%{[docker][container][labels][app]}"
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [January 6, 2019, 7:35pm UTC](https://discuss.elastic.co/t/add-new-field-based-on-another-field/160064/3 "2019-01-06T19:35:54Z")
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